Download 1-What Causes Air Pollution

Air, Atmosphere, and Climate Change
Captivate Audio Script
Slide 2
Air Pollution occurs when harmful substances end up in the air in unhealthy levels. This
is very often the result of human activities but can also come from natural sources such as
volcanoes, dust, pollen, or spores. Pollution that comes from sources related to human
activities are said to come from anthropogenic sources.
Slide 3
There are two main categories of pollutants: primary pollutants and secondary pollutants.
Primary pollutants are put directly into the air by humans. The five main categories of
primary pollutants are as follows:
 Carbon monoxide is produced by incomplete burning of fossil fuels and it
interferes with body’s ability to carry oxygen.
 Nitrogen oxide is formed when fuels burn at temperatures over 538˚C. Nitrogen
oxides contribute to respiratory infections, lung disease, and possibly cancer
 Sulfur dioxide is formed by chemical reactions between sulfur and oxygen, and is
the primary cause of acid precipitation.
 Volatile organic compounds are formed by organic chemicals that vaporize easily
such as gas and paint thinner. These compounds contribute to the formation of
smog and can also cause serious health problems such as cancer.
 Particulate matter consists of tiny particles of liquid or solid matter and can cause
respiratory problems and cancer.
Secondary pollutants are formed when primary pollutants come in contact with other
primary pollutants or with naturally occurring substances and a chemical reaction occurs.
One example of a secondary pollutant is ozone.
Slide 4
Motor vehicles are one major source of anthropogenic air pollution. Currently,
approximately 35% of air pollution comes from motor vehicles. In an effort to reduce air
pollution from motor vehicles congress passed the Clean Air Act in 1970. This act gives
the EPA authority to regulate automobile emissions. The Clean Air Act is responsible for
the elimination of lead in gas and the use of catalytic converters in cars
Industry is another important source of anthropogenic air pollution. Industrial Air
Pollution comes mostly from industries that burn fossil fuels such as electric power
plants, petroleum refineries, auto and airplane manufacturing plants. The Clean Air Act
requires many industries to use pollution control devises
Many times anthropogenic sources of air pollution result in what are called thermal
inversions. This is when air at higher altitudes is warmer than air at lower altitudes. This
is abnormal because normally air temperatures decrease with altitude. Thermal inversions
trap pollution near the Earth’s surface which can lead to the formation of smog.
Slide 5
Exposure by humans to air pollutants can lead to a number of serious health conditions.
Two of these conditions that are normally not fatal but are serious none-the-less are
chronic bronchitis and asthma. Both of these conditions are ongoing inflammation of the
bronchial linings which can eventually make breathing difficult. Chronic bronchitis and
asthma are caused by particulate matter, oxides and acids of sulfur and nitrogen. Two
conditions that are much more serious and can ultimately develop as a result of exposure
to air pollutants are emphysema and lung cancer.
Due to improvements in building techniques and insulation as well as an increase in the
number of chemicals used in the manufacturing process indoor air pollution can
sometimes be worse than outdoor pollution. Indoor air pollution comes from plastics and
other industrial pollutants found in carpets, building materials, paints, cleaning products,
and furniture (just to name a few sources). A condition referred to as sick-building
syndrome occurs in buildings with particularly poor air quality. The best strategy for
preventing sick building syndrome is to ventilate buildings well. Radon Gas, which
occurs naturally as a result of the radioactive decay of uranium is another significant
source of indoor air pollution. Radon gas is generally most concentrated in porous soils
overlying rocks that contain uranium and can lead to cancer. Smokers who are regularly
exposed to radon gas are at a particularly high risk of developing lung cancer as a result
of a synergistic relationship between these two factors.
Side 6
Acid precipitation is defined as rain, sleet, or snow that has a pH of less than 5.6. When
fossil fuels are burned sulfur oxides and nitrogen oxides are released into the atmosphere.
These compounds then come into contact with atmospheric oxygen and sulfuric acid and
nitric acid are formed.
Acid precipitation causes a great deal of harm to ecosystems. First, it can kill aquatic
plants, fish and other animals. Acid precipitation causes aluminum to leach out of the
soil. The aluminum then accumulates on the gills of fish which causes them to slowly
suffocate. Acid shock results when large amounts of acidic water drains into rivers, lakes
or ponds as a result of snow or ice melting. Acid shock can kill entire populations of fish.
In order to offset the effects of the acid precipitation powdered lime can be added to
smaller bodies of fresh water. Unfortunately, often it is not possible to spread enough
lime to offset damage done to lakes.
Acid precipitation is hard to control because it is a global problem. The Helsinki
Declaration, enacted in 1985, requires countries to cut sulfur oxide emissions by 30%.
Although this was a good idea in theory, the Helsinki Declaration was only signed by 18
nations and the U.S. was not one of them. The Sophia Protocol, enacted in 1988, required
a reduction in nitrogen oxide emissions. The Sophia Protocol was initially signed by 27
nations and the U.S. was not included among the original 27. The U.S. finally signed the
Sophia Protocol in 1989.
Slide 7
The atmosphere is a layer of gases that surrounds the Earth and is composed of: 78%
nitrogen, 21% oxygen, and 1% water vapor, argon, carbon dioxide, neon, helium, and
other gases
The earth’s atmosphere is composed of five layers. The troposphere extends from the
surface of the Earth to 10 km above the surface. This layer contains ~90% of all the
Earth’s gases and is where most weather occurs. The stratoshpere extends from 10 km
above the surface to 50 km above the surface and contains the ozone layer. The
mesosphere extends from 50 km above the surface to 80 km above the surface. The
thermosphere extends from 80 km above surface to 500 km above surface. Finally, the
exosphere merges with outer space.
Slide 8
Ozone, the molecule that makes up the ozone layer, is made up of 3 oxygen atoms (O3).
The ozone layer absorbs most of the UV light from the sun. The first signs of the thinning
ozone layer over the South Pole appeared in 1979. By 1997 ozone levels over the
Canadian arctic were down 45%. This allows more UV light to hit the surface of the
Earth which causes various types of damage to all living organisms.
Thinning of the ozone layer is caused by substances that we call ozone eaters.
Chlorofluorocarbons (CFCs) are one type of ozone eater because they break apart in the
Earth’s stratosphere and destroy ozone molecules Most developed countries have banned
the use of CFCs and a fund has been established to help developing countries switch to
CFC alternatives. In addition, many other substances that destroy the ozone have also
been banned
Slide 9
Weather describes short-term changes in various factors in the troposphere such as
amount of sunlight, barometric pressure, cloud cover, precipitation, humidity, and
temperature in a given place at a given time. Climate, on the other hand, describes the
long-term physical characteristics of the troposphere in a given place. Climate is
determined by analyzing weather patterns over a long period of time. The two primary
factors that are used to describe climate are precipitation and temperature.
Slide 10
There are five primary factors that affect climate:
Latitude
Large Bodies of Water
Air Circulation Patterns
Altitude
Topography
Latitude, or distance from the equator, is one of the primary factors that affects the
temperature of a region, and therefore the climate. REMEMBER: climate is determined
primarily by precipitation and temperature. Latitude has a large impact on solar insolation
because as latitude increases the angle of incidence decreases. Large bodies of water help
to moderate the climate of the Earth because of the high specific heat capacity of water
and the circulation of water currents. Air circulation patterns and altitude have an impact
on climate largely as a result of the three key properties of air: warm air rises and cools as
it rises, cool air sinks and warms as it sinks, and warm air holds more water vapor than
cold air. Topographical features such as mountain ranges can have an impact on climate
by influencing how air masses travel and the amount of solar radiation that is absorbed or
reflected.
Slide 11
Global climate remains relatively stable largely as a result of the greenhouse effect. The
Greenhouse Effect is a natural process in which solar radiation is absorbed by greenhouse
gases in the atmosphere thereby warming the Earth’s atmosphere and surface. Absorption
of small quantities of radiation is good, because it provides the warmth needed on Earth
for living organisms to survive. Without the greenhouse effect the average temperature of
the earth would be between -15˚C and -20˚ C. If greenhouse gases absorb too much
radiation the result is an acceleration or enhancement of the greenhouse effect which
could cause an increase in the average temperature of the earth.
Slide 12
Global warming is an increase in average global temperatures as a result of an increase in
the concentration of greenhouse gases in the atmosphere due to human activities. Since
the industrial revolution scientists have seen a drastic increase in the concentrations of
many greenhouses, most notably carbon dioxide and methane.
Global warming, unfortunately, is a self-perpetuating cycle. This means that once it has
begun it is very difficult to stop or even slow down. Warmer land surface area causes
higher evaporation, which then causes an increase of water vapor. In addition, warmer
land surface area causes an increase in air temperature. Higher air temperatures also
cause ice caps to melt, which then causes more solar radiation reaching the Earth. In
addition, warmer air temperatures cause an increase in the average temperature of large
bodies of water. This accelerates the melting of glacial ice. The melting of ice caps and
glaciers leads to further warming of air and ocean temperatures..... etc. etc.